Welding flux



United States Patent 3,340,107 WELDING FLUX John T. Ballass and Bernard J. Freedman, Groton, Conn., assignors to General Dynamics Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed Apr. 29, 1965, Ser. No. 452,023 2 Claims. (Cl. 148-26) ABSTRACT OF THE DISCLOSURE A welding flux in which the flux ingredients consist essentially of, by weight from about 5% to about 15% aluminum oxide, up to about 15% manganous oxide, from about 20% to about 55% sodium fluoride, and the balance being essentially silicon dioxide and calcium oxide in an approximate ratio by weight of silicon dioxide to calcium oxide within the range of about 2:1 to about 1:1. The flux is particularly suited for use in the welding of low alloy, high strength steels and provides significantly improved mechanical properties and a weldment having a smooth finish.

This invention relates to welding flux and, in particular, to a welding flux suitable for use in the welding of low alloy, high strength steels.

To obtain a high quality weldment, it is necessary that a welding flux be utilized in order to provide a protective covering for the metal at the welding site to prevent oxidation of and other undesirable changes in the metal during welding. The particular welding flux utilized depends upon the type of metal being welded and upon the Welding process used.

The welding flux of the present invention is intended for use in welding steel, and especially low alloy, high strength steels. While it is satisfactory for a number of welding techniques, for example, the Electro-Slag method, itis particularly well suited for use in the submerged-arc welding process. The submerged-arc welding process employs a blanket of molten flux to shield a weldingwire electrode and the moltenbase metal of the parts being welded from the atmosphere. Fluxes used in submerged arc processes are compositions of granular fusible materials which are deposited onto the work around the end of the Wire electrode and the base metal in the region of melting. The submerged-arc process is widely,

used because of its advantages, among others, of being readily adapted to the use of automatic equipment, of being carried out at speeds significantly higher than most other known welding techniques and of providing welds of large thickness.

In our copending applications (1) for Welding Flux, Ser. No. 127,485 filed July 28, 1961, now Patent No. 3,192,076, and (2) for Welding Flux, Ser. No. 196,875 filed May 23, 1962, now Patent No. 3,192,077, we have disclosed welding fluxes particularly well suited for low alloy, high strength steels which provide Welds havingparticularly high notch toughnesses and other mechanical properties. While the fluxes as disclosed in those applications are entirely satisfactory, they are expensive to make.

We have now discovered a novel and improved weld- V ing flux which is significantly less costly than fluxes of our previous applications referred to above and which provides welds having mechanical properties generally comparable to those obtained using the fluxes of those applications. Because the flux of the present invention is low in cost, it is also of practical use in welding low grade steels as well as for high strength steels. The new flux provides welds having especially high strength and a high notch toughness. Additionally, the new flux is "ice sufliciently fluid when fused during the welding operation to produce a reasonably smooth surface on the weld.

The welding flux of the present invention comprises a mixture consisting essentially of by weight 5 to 15 aluminum oxide (A1 0 up to 15% manganous oxide (MnO), 20 to 55 sodium fluoride (NaF) and the balance silicon dioxide (SiO and calcium oxide (CaO), the latter two ingredients being present in amounts within the range of proportion by weight of SiO,, to CaO of from about 2:1 to about 1:1.

The raw materials used in preparing the fluxes of the invention are preferably of the usual commercial purity, although incidental impurities do not usually afiect the function of the welding flux appreciably. The raw materials are preferably of a particle size such that all pass through a 50 mesh screen. To prepare the fluxes, silica, lime, alumina, manganous oxide, and sodium fluoride are combined in preselected proportions and mixed in the dry state to obtain a uniform mixture. The silica may be of a mineral grade containing at least Si0 and a maximum of 5% aluminum. The lime may also be of a commercial grade and contain at least 92% CaO after drying at 2000 F., and it may also contain a maximum of 1.5% magnesium and 2% aluminum. The manganous oxide may also be of a commercial grade containing a minimum Mn content of 45%, maximum Fe content of 8%, a maximum Al content of 5%, a maximum content of 1% of Zn, As and Pb and a maximum Ba content of 2%. The alumina is calcined, is of a commercial grade, and contains 99% A1 0 after drying at 2000 F. The sodium fluoride may be of a technical grade containing: at least NaF.

The welding flux of this invention may be made utilizing the above mentionedraw materials by any of the conventional methods employed in the art, that is, by the fusion, the sintering, or the bondingmethods.

In the fusion technique, the raw materials are mechanically mixed with each other and the mixtureplaced in a graphite crucible and heated to about 2400 to 2600 F. until it melts. After heating the molten mixture for about 20 more minutes to ensure complete fusion, it is quenched to room temperature and then ground and crushed.

To produce the flux by the sintering technique, a mechanical mixture of theconstituents is heated in an oven at about 1650 F. for about 1 /2 hours. The mixture is then cooled, crushed, screened to obtainthe desiredparticle distribution and used in the same manner as the fused materials.

When the flux is prepared according to a bonding technique, the mixture ofv constituents is combined with water glass in a ratio of about one part of water glass to three parts of the flux mixture. This mass is then heated to 900 F. for about three hours, crushed, screened, and employed in the usual manner. Of the three suitable methods for preparing the flux, the fusion technique is generally preferred.

Table 1 below lists a number of specific examples of the welding flux of the present invention which have been prepared by the fusion method. The analyses were determined on the constituent mixtures prior to fusion.

TABLE l.-ANALYSIS OF FLUX PERCENT BY WEIGHT The foregoing flux compositions were utilized to weld HY-80 steel, which is an exemplary high strength low TABLE 2.MEGHANICAL PROPERTIES OF WELD METAL Charpy V-Notch Impact Toughness Impact Energy in ft. lbs. Welding Flux Tensile Yieglfistigength Elonggtilorz iteduction of; V

St en th, .s.i. 0.2 se .s.i. ercen rea, pereen a r g p p p Room Temp. F. -eo F. -so r.

alloy steel having a yield strength (0.2% offset) of be tween about 80,000 and 100,000 p.s.i. HY-80 steel has the following chemical composition:

The complete specifications of HY-80 steel may be found in U.S. Government specification MIL-S-l6216D (Navy).

The welds were made utilizing a welding wire inch in diameter, and having the following chemical analysis in percent by weight.

Element: Percentage by weight C .09 S .004 P .006 Si .74 Mn 1.40 Cr .04 Ni 1.03 Cu .48; Mo .28 Zr .076

Welds were made with the above-described 3/3 inch diameter welding wire in 1 inch thick HY-80 steel plates with a single vee 45 bevel groove butt joint, and mechanical tests, the. results of which are set forth in Table 2, were made. A heat input of 44,500. joules/inch was. provided by direct current reverse polarity at 550? amperes, arc current, and 27 volts, arc voltage, with the electrode moving along at the weld joint at inches per minute. Another weld using flux C was made inv the same manner but at a heat input of about 54,000 joules/ inch provided by direct current reverse polarity at 600 amperes arc current, and 30 volts, arc voltage, and the -test results for this weld are designated by an asterisk in Table 2. The welding wire electrodes were bare metal, and' the granulated flux was. supplied to the weld in sufiicient quantities by gravity feed concentric with the welding electrode.

It is apparent from Table 2 that the welding flux of the invention provides a weld having mechanical properties similar to those of the base metal. Of particular interest is the high notch toughness of the welds obtained utilizing the Welding flux of the invention. From the data, it is evident that the preferred flux composition is represented by fluxes B and C.

The flux of this invention may be used in other welding methods, for example, the flux can be used as the flux core of' a hollow tubular welding wire. Further, the addition of certain materials to the flux core which form a vapor shield over the welding site is contemplated, such as in the method described in the article by R. A. Wilson in Welding Journal, vol. 40, No. 1, January 1961. Furthermore, the flux of this invention can be mixed with metallic particles having, for example, the same analysis as the welding wire or as the steel being joined. This type of flux mixture is well known in the art, and because it is attracted to the welding site by magnetism in electric welding, it can be used in situations Where a gravity feed of flux cannot be provided. It will be understood by those skilled in the art that the above-described embodiments of the inventionare exemplary and that many variations and modifications thereof can be made by those skilled in the art without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention as defined in the appended claims.

We claim:

1. A welding flux in which the fluxing ingredients consist essentially of, by weight, from about 5% to about 15% aluminum oxide, up to about 15% manganous oxide, from about 20% to about 55% sodium fluoride, and the balance being essentially silicon dioxide and calcium oxide in an approximate ratio by weight of silicon dioxide to calcium oxide within the range of about 2:1 to about 1*:1.

2. A welding, flux in which the fluxing ingredients consist essentially of, by weight, from about 5% to about 15 aluminum oxide, up to about 15 manganous oxide, from about 40% to about 45% sodium fluoride, and the balance being essentially silicon dioxide and calcium oxide in an approximate ratio by weight of silicon dioxide to calcium oxide within the range of about 2:1 to about 1:1.

References Cited UNITEDv STATES PATENTS .HYL D BIZQT ima Examiner- DAVID L. RECK, Examiner.

H. F. SAITO, Assistant Examiner. 

1. A WELDING FLUX IN WHICH THE FLUXING INGREDIENTS CONSIST ESSENTIALLY OF, BY WEIGHT, FROM ABOUT 5% TO ABOUT 15% ALUMINUM OXIDE, UP TO ABOUT 15% MANGANOUS OXIDE, FROM ABOUT 20% TO ABOUT 55% SODIUM FLUORIDE, AND THE BALANCE BEING ESSENTIALLY SILICON DIOXIDE AND CALCIUM OXIDE IN AN APPROXIMATE RATIO BY WEIGHT OF SILICON DIOXIDE TO CALCIUM OXIDE WITHIN THE RANGE OF ABOUT 2:1 TO ABOUT 1:1. 